A core drilling machine uses a cylindrical diamond-tipped drill bit to cut a ring-shaped groove into a workpiece that is to be worked in order to create a cylindrical drill core there which can then be removed in its entirety from the drilled hole. The material can be, for example, concrete, masonry, stone or the like.
Numerous technical problems can arise during the individual phases of a core drilling procedure. Particularly during the so-called spot-drilling phase, that is to say, the phase when the drill bit is placed onto the workpiece that is to be worked and the core drilling procedure is started, undesired oscillations or vibrations can be exerted onto the drill bit and onto the core drilling machine. These oscillations or vibrations can often also lead to resonances in the drill bit and in the core drilling machine, thereby greatly impairing the drilling procedure.
These oscillations or vibrations and ultimately also the resonances usually arise in that, during the early phase of the core drilling procedure (spot-drilling phase), the drill bit has not yet penetrated deep enough into the material that is to be worked and therefore, the rotating drill bit is not yet being sufficiently guided in the hole that is being drilled. However, it can also be the case that, during later phases of the core drilling procedure, when the drill bit apparently already has sufficient guidance in the hole being drilled, undesired oscillations or vibrations and consequently also resonances might occur. Even during these later drilling phases, these oscillations, vibrations and resonances lead to insufficient operation.
Generally speaking, oscillations, vibrations and resonances should be avoided during a core drilling procedure since they exert severe mechanical and dynamic loads on the drilling tools which, in turn, can give cause damage to the drill bit, to the drilling machine and/or to the drill stand. Moreover, this can translate into poor drilling results in the form of crooked drilled holes that do not run at the prescribed angle (e.g. 90°) relative to the surface of the material that is to be worked.
Furthermore, these oscillations, vibrations and resonances also entail certain safety risks. A user could be tempted to try to provisionally reduce the vibrations, that is to say, by placing auxiliary means onto the drill bit, for example, the user's own foot. This, however, might cause injury to the user and/or cause damage to the core drilling machine.
As a measure aimed at avoiding the undesired oscillations and vibrations, the rotational speed of the drill drive and thus the drilling speed are usually reduced, as a result of which the drill advances altogether more slowly. As a consequence, the core drilling procedure is prolonged, thus rendering the drilling procedure altogether inefficient.